Coated article with low-E coating having absorbing layers for low film side reflectance and low visible transmission

ABSTRACT

Absorbing layers of a low-emissivity (low-E) coating are designed to cause the coating to have a reduced film side reflectance which is advantageous for aesthetic purposes. In certain embodiments, the absorbing layers are metallic or substantially metallic (e.g., NiCr or NiCrN x ) and are positioned in order to reduce or prevent oxidation of the absorbing layers during optional heat treatment (e.g., thermal tempering, heat bending, and/or heat strengthening). Coated articles according to certain example embodiments of this invention may be used in the context of insulating glass (IG) window units, other types of windows, etc.

This invention relates to a coated article including a low-emissivity(low-E) coating. In certain example embodiments, absorbing layers of thelow-E coating are positioned/designed to cause the coating to have both(i) a low visible transmission (e.g., no greater than 45%, morepreferably no greater than 40%, and most preferably no greater than35%), and (ii) a reduced visible film side reflectance. An upperabsorbing layer may be provided in an upper stack and another absorbinglayer may be provided in a middle stack of the low-E coating. In certainexample embodiments, the absorbing layers are metallic or substantiallymetallic. The absorbing layer in the middle stack may be providedbetween first and second nitride layers (e.g., silicon nitride basedlayers), whereas the absorbing layer in the upper stack may be providedbetween a nitride layer and a metallic or substantially metallicinfrared (IR) reflecting layer, in order to reduce or prevent oxidationof the absorbing layers during optional heat treatment (e.g., thermaltempering, heat bending, and/or heat strengthening) and/or manufacturingthereby permitting predictable coloration and optical characteristics tobe achieved. Coated articles according to certain example embodiments ofthis invention may be used in the context of insulating glass (IG)window units, vehicle windows, other types of windows, or in any othersuitable application.

BACKGROUND OF THE INVENTION

Coated articles are known in the art for use in window applications suchas insulating glass (IG) window units, vehicle windows, and/or the like.It is known that in certain instances, it is desirable to heat treat(e.g., thermally temper, heat bend and/or heat strengthen) such coatedarticles for purposes of tempering, bending, or the like in certainexample instances. Heat treatment of coated articles typically requiresuse of temperature(s) of at least 580 degrees C., more preferably of atleast about 600 degrees C. and still more preferably of at least 620degrees C. Such high temperatures (e.g., for 5-10 minutes or more) oftencause coatings to break down and/or deteriorate or change in anunpredictable manner. Thus, it is desirable for coatings to be able towithstand such heat treatments (e.g., thermal tempering), if desired, ina predictable manner that does not significantly damage the coating.

In certain situations, designers of coated articles strive for acombination of desirable visible transmission, desirable color, lowemissivity (or emittance), and low sheet resistance (R_(S)).Low-emissivity (low-E) and low sheet resistance characteristics permitsuch coated articles to block significant amounts of IR radiation so asto reduce for example undesirable heating of vehicle or buildinginteriors. Often, more IR radiation being blocked (including reflected)is accompanied by less visible transmission.

U.S. Pat. No. 7,597,965 discloses a low-E coating with an NiCr absorberlayer in the lower dielectric stack. However, the example coating in the'965 patent is designed for a high visible transmission, and indeed hasa visible transmission (T_(vis) or TY) of 59%. Lower visibletransmissions are often desirable. For example, it is often desirablefor aesthetic and/or optical purposes to provide coated articles(including low-E coatings) having visible transmissions of no greaterthan 45%, more preferably no greater than 40%, and sometimes no greaterthan about 35%. However, when visible transmission of a coated articleis reduced via a low-E coating design, the film side reflectance of thecoating typically increases.

U.S. Pat. No. 7,648,769 discloses a low-E coating with an NiCr absorberlayer provided in the middle dielectric stack, but not in the upper andlower dielectric stacks of the coating (e.g., see FIG. 1 of the '769patent). Example 1 in the '769 patent realizes, measured monolithically,a visible transmission of 54.5% and a film side reflectance of 19.5%,and when measured in an insulating glass (IG) window unit the valueschange to a visible transmission of 50% and a film side reflectance of23%. Example 2 in the '769 patent has a higher visible transmission andrealizes, measured monolithically, a visible transmission of 67.5% and afilm side reflectance of 11.5%, and when measured in an insulating glass(IG) window unit the values change to a visible transmission of 62% anda film side reflectance of 17%. The examples in the '769 patent teachthat when visible transmission goes down, film side reflectance goes up.

It will also be explained herein, in the detailed description section,that providing a given absorber layer only in the middle dielectricstack of a low-E coating having a visible transmission of about 40%results in an undesirably high visible film side reflectance (RfY) ofover 30% (measured monolithically).

Thus, it will be appreciated that it has been difficult to achievecoated articles, including low-E coatings, having a combination of both(i) desirably low visible transmission, and (ii) low film sidereflectance. It will be apparent to those skilled in the art that thereexists a need in the art for a coated article having low emissivity (orlow sheet resistance) and a combination of both low visible transmission(e.g., no greater than 45%, more preferably no greater than about 40%,and most preferably no greater than about 35%) and low film sidereflectance.

BRIEF SUMMARY OF EXAMPLE EMBODIMENTS OF THE INVENTION

A coated article includes a low-E coating. In certain exampleembodiments, absorbing layers in the low-E coating arepositioned/designed to cause the low-E coating to have both (i) a lowvisible transmission (e.g., no greater than 45%, more preferably nogreater than 40%, and most preferably no greater than 35%), and (ii) lowvisible film side reflectance which is advantageous for aestheticpurposes. An absorbing layer is be provided in an upper stack of thelow-E coating and another absorbing layer is provided in a middle stackof the low-E coating, and in certain double-silver embodiments nosimilar absorbing layer is provided in the lower stack of the low-Ecoating. The absorbing layers are metallic or substantially metallic(e.g., NiCr or NiCrN_(x)). In certain example embodiments the absorbinglayer in the middle stack is provided between first and second nitridelayers (e.g., silicon nitride based layers), and the absorbing layer inthe upper stack is provided between a nitride layer and a metallic orsubstantially metallic infrared (IR) reflecting layer, in order toreduce or prevent oxidation of the absorbing layers during optional heattreatment (e.g., thermal tempering, heat bending, and/or heatstrengthening) and/or manufacturing thereby permitting predictablecoloration and optical characteristics to be achieved. It has been foundthat the use of such absorbing layers in the top and middle portions ofthe coating surprisingly and unexpectedly allows for a combination oflow visible transmission and low film side reflectance to besimultaneously realized. Coated articles according to certain exampleembodiments of this invention may be used in the context of IG windowunits, vehicle windows, other types of windows, or in any other suitableapplication.

In certain example embodiments of this invention, there is provided acoated article including a coating supported by a glass substrate, thecoating comprising: first and second infrared (IR) reflecting layers(e.g., of or including silver), wherein said IR reflecting layers arespaced apart from one another, and wherein the first IR reflecting layeris located closer to the glass substrate than is the second IRreflecting layer; a first substantially metallic or metallic absorptionlayer (e.g., of or including NiCr and/or NiCrN_(x)) located such thatthe first absorption layer is located between the first and second IRreflecting layers, wherein the first absorption layer is sandwichedbetween and contacting first and second dielectric layers comprisingsilicon nitride; and a second substantially metallic or metallicabsorption layer (e.g., of or including NiCr and/or NiCrN_(x)) locatedsuch that both the first and second IR reflecting layers are locatedbetween the glass substrate and the second absorption layer, wherein thesecond absorption layer is located between and contacting the second IRreflecting layer and a third dielectric layer comprising siliconnitride.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a coated article according to anexample embodiment of this invention.

FIG. 2 is a cross sectional view showing the coated article of FIG. 1provided in an IG window unit according to an example embodiment of thisinvention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

Coated articles herein may be used in applications such as IG windowunits, vehicle windows, monolithic architectural windows, residentialwindows, and/or any other suitable application that includes single ormultiple glass substrates.

In certain example embodiments of this invention, the coating includes adouble-silver stack (as shown in FIG. 1), although this invention is notso limited in all instances.

For example, in certain example embodiments of this invention, heattreated or non-heat-treated coated articles having multiple IRreflecting layers (e.g., two spaced apart silver based layers) arecapable of realizing a sheet resistance (R_(S)) of less than or equal to3.0 (more preferably less than or equal to 2.5, even more preferablyless than or equal to 2.1, and most preferably less than or equal to2.0). The terms “heat treatment” and “heat treating” as used herein meanheating the article to a temperature sufficient to achieve thermaltempering, heat bending, and/or heat strengthening of the glassinclusive article. This definition includes, for example, heating acoated article in an oven or furnace at a temperature of least about 580degrees C., more preferably at least about 600 degrees C., for asufficient period to allow tempering, bending, and/or heatstrengthening. In certain instances, the HT may be for at least about 4or 5 minutes. The coated article may or may not be heat treated indifferent embodiments of this invention.

FIG. 1 is a side cross sectional view of a coated article according toan example non-limiting embodiment of this invention. The coated articleincludes substrate 1 (e.g., clear, green, bronze, or blue-green glasssubstrate from about 1.0 to 10.0 mm thick, more preferably from about1.0 mm to 3.5 mm thick), and low-E coating (or layer system) 30 providedon the substrate 1 either directly or indirectly. The coating (or layersystem) 30 includes, for example: bottom dielectric silicon nitridelayer 3 which may be Si₃N₄, of the Si-rich type for haze reduction, orof any other suitable stoichiometry silicon nitride in differentembodiments of this invention, first lower contact layer 7 (whichcontacts bottom IR reflecting layer 9), first conductive and preferablymetallic or substantially metallic infrared (IR) reflecting layer 9,first upper contact layer 11 (which contacts layer 9), dielectric layer13, dielectric silicon nitride based and/or inclusive layer 14, metallicor substantially metallic absorbing layer 4 (e.g., of or including NiCr,NiCrN_(x), or the like), additional dielectric silicon nitride layer 14′which may be Si₃N₄, of the Si-rich type for haze reduction, or of anyother suitable stoichiometry silicon nitride, tin oxide inclusive basedand/or inclusive interlayer 15, second lower contact layer 17 (whichcontacts IR reflecting layer 19), second conductive and preferablymetallic or substantially metallic IR reflecting layer 19, metallic orsubstantially metallic absorbing layer 25 (e.g., of or including NiCr,NiCrN_(x), or the like) which is located over and contacting the upperIR reflecting layer 19, and overcoat dielectric silicon nitride layer 26which may be Si₃N₄, of the Si-rich type for haze reduction, or of anyother suitable stoichiometry silicon nitride. The “contact” layers 7,11, and 17 each contact at least one IR reflecting layer (e.g., layerbased on Ag). The aforesaid sputter-deposited layers 3-26 make up low-E,(i.e., low emissivity) coating 30 that is provided on glass or plasticsubstrate 1.

In monolithic instances, the coated article includes only one glasssubstrate 1 as illustrated in FIG. 1. However, monolithic coatedarticles herein may be used in devices such as laminated vehiclewindshields, IG window units, and the like. As for IG window units, anIG window unit may include two spaced apart glass substrates. An exampleIG window unit is illustrated and described, for example, in U.S. PatentDocument No. 2004/0005467, the disclosure of which is herebyincorporated herein by reference. FIG. 2 shows an example IG window unitincluding the coated glass substrate shown in FIG. 1 coupled to anotherglass substrate 2 via spacer(s), sealant(s) 40 or the like, with a gap50 being defined therebetween. This gap 50 between the substrates in IGunit embodiments may in certain instances be filled with a gas such asargon (Ar) (in addition to including air). An example IG unit maycomprise a pair of spaced apart clear glass substrates each about 3-6 mmthick, one of which is coated with a coating 30 herein in certainexample instances, where the gap 50 between the substrates may be fromabout 5 to 30 mm, more preferably from about 10 to 20 mm, and mostpreferably about 16 mm. In certain example instances, the coating 30 maybe provided on the interior surface of either substrate facing the gap(the coating is shown on the interior major surface of substrate 1 inFIG. 2 facing the gap 50, but instead could be on the interior majorsurface of substrate 2 facing the gap 50). Either substrate 1 orsubstrate 2 may be the outermost substrate of the IG window unit at thebuilding exterior (e.g., in FIG. 2 the substrate 1 is the substrateclosest to the building exterior).

Absorption layer 4 is, in certain example embodiments of this invention,located between and contacting nitride based dielectric layers 14 and14′. In certain example embodiments, each of layers 14 and 14′surrounding the absorption layer 4 is a nitride layer and issubstantially or entirely non-oxidized. Absorption layer 25 is, incertain example embodiments of this invention, located between andcontacting the metallic or substantially metallic IR reflecting layer 19and nitride based dielectric layer 26. In certain example embodiments,each of layers 19 and 26 surrounding the absorption layer 25 issubstantially or entirely non-oxidized. Optionally, the outermostportion of layer 26 may be oxided if it is the outermost layer of thecoating 30 and exposed to atmosphere. The use of nitride layers 14, 14′and 26, and metallic or substantially metallic layer 19, around theabsorber layers 4 and 25 is advantageous in that it helps prevent (orreduce the likelihood of) the absorption layers 4, 25 from beingoxidized during heat treatment, thereby better allowing the absorptionlayers 4, 25 to perform an intended function, in particular absorbing atleast some amount (e.g., at least 5%, more preferably at least 10%) ofvisible light. It will be appreciated that if a layer becomes toooxidized during heat treatment or the like, it no longer can function asan adequate absorption layer.

In certain example embodiments of this invention, absorption layers 4and 25 may be of or include NiCr (any suitable ratio or Ni:Cr), and mayor may not be nitrided (NiCrN_(x)). Absorption layers 4 and 25 arelocated between and contacting substantially non-oxided layers as shownin FIG. 1. In certain example embodiments, each of the nitride basedlayers 14, 14′, 26 surrounding the absorption layers 4, 25 is a nitridelayer and is substantially or entirely non-oxidized, and IR reflectinglayer 19 is also substantially or entirely non-oxidized. In certainexample embodiments, absorption layers 4, 25 may comprise from 0-10%oxygen, more preferably from 0-5% oxygen, and most preferably from 0-2%oxygen (atomic %). In certain example embodiments, one or bothabsorption layers 4, 25 comprise from 0-20% nitrogen, more preferablyfrom 1-15% nitrogen, and most preferably from about 1-12% nitrogen(atomic %). While NiCr is a preferred material for the absorption layers4 and 25, it is possible that other materials may instead be used. Forexample, in certain other heat treatable example embodiments of thisinvention, the absorption layers 4 and/or 25 may be of or include Ni,Cr, NiCrN_(x), CrN, ZrN, or TiN. In non-heat treatable embodiments, anyof the aforesaid materials may be used for the absorption/absorbinglayers 4 and/or 25, as well as other materials such as Ti, Zr, NiOx orthe like.

The absorbing layers 4 and 25 of the low-E coating 30 are de signed tocause the coating 30 to have a lower visible transmission, desirablecoloration, and low film side reflectance. In certain exampleembodiments, the metallic or substantially metallic absorbing layer(e.g., NiCr or NiCrN_(x)) 4 may be from about 20-120 angstroms (Å)thick, more preferably from about 35-75 angstroms (Å) thick, and mostpreferably from about 50-70 angstroms (Å) thick. In certain exampleembodiments, the upper metallic or substantially metallic absorbinglayer (e.g., NiCr or NiCrN_(x)) 25 may be from about 15-70 angstroms (Å)thick, more preferably from about 23-48 angstroms (Å) thick, and mostpreferably from about 27-43 angstroms (Å) thick. In certain exampleembodiments, the upper absorbing layer 25 may be thinner than the lowerabsorbing layer 4. For example, in certain example embodiments, theupper absorbing layer 25 may be at least 10 angstroms (Å) thinner (morepreferably at least 20 angstroms thinner) than the lower absorbing layer4, in order to provide for desirable optical characteristics of thecoated article. It has been found that a combination of low visibletransmission, reduced visible film side reflectance, and desirableoptical characteristics can be achieved by having absorber layers bothin the middle dielectric portion of the stack (see absorber layer 4) andby providing another absorber layer 25 in the upper portion of the stackabove the top IR reflecting layer 19, as it has been found that movingsignificant absorption to the top of the stack via layer 25 results inreduced film side reflectance compared to providing absorber layer onlybetween the IR reflecting layers, while still allowing for desirableoptical characteristics such as color at angle, etc. via absorptionlayer 4 in the middle portion of the stack.

Thus, an absorbing layer 25 is provided in the upper stack (above theupper Ag based IR reflecting layer 19), and a second absorbing layer 4is provided in the middle portion of the stack (between the IRreflecting layers 9, 19). Preferably, in certain double-silverembodiments (i.e., where the low-E coating has two Ag-based IRreflecting layers), no similar absorbing layer is provided below thelower IR reflecting layer 9. In other words, while absorber layers 4 and25 are provided in middle and upper portions of the coating, there is nosimilar absorber layer between nitrides provided below the bottom IRreflecting layer 9.

Dielectric layers 3, 14, 14′ and 26 may be of or include silicon nitridein certain embodiments of this invention. Silicon nitride layers 3, 14,14′ and 26 may, among other things, improve heat-treatability of thecoated articles and protect the absorbing layers during optional HT,e.g., such as thermal tempering or the like. One or more of the siliconnitride of layers 3, 14, 14′ and 26 may be of the stoichiometric type(i.e., Si₃N₄), or alternatively of the Si-rich type of silicon nitridein different embodiments of this invention. The presence of free Si in aSi-rich silicon nitride inclusive layer 3 may allow certain atoms suchas sodium (Na) which migrate outwardly from the glass 1 during HT to bemore efficiently stopped by the Si-rich silicon nitride inclusivelayer(s) before they can reach the silver 9 and damage the same. It isbelieved that the Si-rich Si_(x)N_(y) can reduce the amount of damagedone to the silver layer(s) during HT in certain example embodiments ofthis invention thereby allowing sheet resistance (R_(S)) to decrease orremain about the same in a satisfactory manner. Moreover, it is believedthat the Si-rich Si_(x)N_(y) can reduce the amount of damage (e.g.,oxidation) done to absorbing layer 4 (and/or 25) during HT in certainexample optional embodiments of this invention. In certain exampleembodiments, when Si-rich silicon nitride is used, the Si-rich siliconnitride layer as deposited may be characterized by Si_(x)N_(y) layer(s),where x/y may be from 0.76 to 1.5, more preferably from 0.8 to 1.4,still more preferably from 0.82 to 1.2. Moreover, in certain exampleembodiments, before and/or after HT the Si-rich Si_(x)N_(y) layer(s) mayhave an index of refraction “n” of at least 2.05, more preferably of atleast 2.07, and sometimes at least 2.10 (e.g., 632 nm) (note:stoichiometric Si₃N₄ which may also be used has an index “n” of2.02-2.04). It is noted that n and k tend to drop due to heat treatment.Any and/or all of the silicon nitride layers discussed herein may bedoped with other materials such as stainless steel or aluminum incertain example embodiments of this invention. For example, any and/orall silicon nitride layers discussed herein may optionally include fromabout 0-15% aluminum, more preferably from about 1 to 10% aluminum, incertain example embodiments of this invention. The silicon nitride maybe deposited by sputtering a target of Si or SiAl, in an atmospherehaving argon and nitrogen gas, in certain embodiments of this invention.Small amounts of oxygen may also be provided in certain instances in thesilicon nitride layers.

Infrared (IR) reflecting layers 9 and 19 are preferably substantially orentirely metallic and/or conductive, and may comprise or consistessentially of silver (Ag), gold, or any other suitable IR reflectingmaterial. IR reflecting layers 9 and 19 help allow the coating to havelow-E and/or good solar control characteristics. The IR reflectinglayers may, however, be slightly oxidized in certain embodiments of thisinvention.

Contact layer 11 may be of or include nickel (Ni) oxide, chromium/chrome(Cr) oxide, NiCr, or a nickel alloy oxide such as nickel chrome oxide(NiCrO_(x)), or other suitable material(s), in certain exampleembodiments of this invention. The use of for example, NiCrO_(x) inlayer 11 allows durability to be improved. The NiCrO_(x) of layer 11 maybe fully oxidized in certain embodiments of this invention (i.e., fullystoichiometric), or alternatively may only be partially oxidized. Incertain instances, the NiCrO_(x) layer 11 may be at least about 50%oxidized. Contact layer 11 (e.g., of or including an oxide of Ni and/orCr) may or may not be oxidation graded in different embodiments of thisinvention. Oxidation grading means that the degree of oxidation in thelayer changes throughout the thickness of the layer so that for examplea contact layer may be graded so as to be less oxidized at the contactinterface with the immediately adjacent IR reflecting layer 9 than at aportion of the contact layer(s) further or more/most distant from theimmediately adjacent IR reflecting layer. Descriptions of various typesof oxidation graded contact layers are set forth in U.S. Pat. No.6,576,349, the disclosure of which is hereby incorporated herein byreference. Contact layer 11 (e.g., of or including an oxide of Ni and/orCr) may or may not be continuous in different embodiments of thisinvention across the entire IR reflecting layer 9. In certainalternative example embodiments of this invention, layer 11 may insteadbe made as a metallic or substantially metallic absorption layer (e.g.,NiCr or NiCrN_(x)) like layer 25.

Dielectric layers 13 and 15 may be of or include tin oxide in certainexample embodiments of this invention. However, as with other layersherein, other materials may be used in different instances. Interlayer15 of or including tin oxide is provided under IR reflecting layer 19 soas to be located between silicon nitride layer 14′ and zinc oxide layer17. The use of such a tin oxide inclusive interlayer 15 results innumerous improvements compared to a situation where the layer is notprovided. For example, it has been found that the use of such a tinoxide inclusive interlayer 15 results in a coated article which iscapable of realizing: (a) less visible transmission shift due to heattreatment, (b) higher visible transmission following heat treatment; (c)less shifting of certain color value(s) due to heat treatment, (d)substantially neutral coloration following heat treatment; (e) morestable, or even decreasing, sheet resistance due to heat treatment, (f)lower sheet resistance and thus lower emissivity following heattreatment, (g) improved haze characteristics following heat treatment,and/or (h) improved mechanical durability such as scratch resistancebefore and/or after heat treatment. Thus, in certain example embodimentsof this invention, coated articles may be taken to higher temperaturesduring heat treatment and/or for longer times without sufferingundesirable significant transmission drops and/or increases in sheetresistance. In certain alternative embodiments, it is possible to dopethe tin oxide of layer 15 with other materials such as Al, Zn or thelike. Alternatively, other metal oxide(s) may be used for layer 15 incertain instances.

Lower contact layers 7 and/or 17 in certain embodiments of thisinvention are of or include zinc oxide (e.g., ZnO). The zinc oxide oflayers 7 and 17 may contain other materials as well such as Al (e.g., toform ZnAlO_(x)). For example, in certain example embodiments of thisinvention, one or more of zinc oxide layers 7, 17 may be doped with fromabout 1 to 10% Al, more preferably from about 1 to 5% Al, and mostpreferably about 1 to 4% Al.

Other layer(s) below or above the illustrated coating may also beprovided. Thus, while the layer system or coating is on or “supportedby” substrate 1 (directly or indirectly), other layer(s) may be providedtherebetween. Thus, for example, the coating of FIG. 1 may be considered“on” and “supported by” the substrate 1 even if other layer(s) areprovided between layer 3 and substrate 1. Moreover, certain layers ofthe illustrated coating may be removed in certain embodiments, whileothers may be added between the various layers or the various layer(s)may be split with other layer(s) added between the split sections inother embodiments of this invention without departing from the overallspirit of certain embodiments of this invention.

While various thicknesses and materials may be used in layers indifferent embodiments of this invention, example thicknesses andmaterials for the respective layers on the glass substrate 1 in the FIG.1 embodiment are as follows, from the glass substrate outwardly (notethat the NiCr layers may or may not be partially nitrided):

Example Materials/Thicknesses; FIG. 1 Embodiment Layer Glass PreferredMore Example (1-10 mm thick) Range (Å) Preferred (Å) (Å) Si_(x)N_(y)(layer 3) 40-750 Å    250-600 Å 419 Å ZnO_(x) (layer 7) 10-300 Å    60-150 Å 80 Å Ag (layer 9) 50-200 Å     80-130 Å 119 Å NiCrO_(x) (layer11) 10-100 Å    12-40 Å 25 Å SnO₂ (layer 13) 0-1,000 Å 200-700 Å 545 ÅSi_(x)N_(y) (layer 14) 50-450 Å     80-200 Å 120 Å NiCr (layer 4) 35-75Å     50-70 Å 62 Å Si_(x)N_(y) (layer 14′) 40-450 Å     70-300 Å 151 ÅSnO₂ (layer 15) 30-250 Å     50-200 Å 80 Å ZnO_(x) (layer 17) 10-300Å     40-130 Å 80 Å Ag (layer 19) 50-200 Å     70-180 Å 153 Å NiCr(layer 25) 23-48 Å     27-43 Å 35 Å Si_(x)N_(y) (layer 26) 40-500 Å    70-400 Å 317 Å

It can be seen that the bottom absorber layer 4 is thicker than theupper absorber layer 25. For example, in certain embodiments the bottomabsorber layer 4 is at least 10 Å thicker than the upper absorber layer25, more preferably at least 20 Å thicker, and even more preferably atleast 25 Å thicker. Also, it can be seen that for absorber layer 4, thebottom silicon nitride layer 14 is thinner than the top silicon nitridelayer 14′. For example, surrounding absorber layer 4, in certainembodiments the bottom silicon nitride layer 14 is at least 10 Å thinnerthan the top silicon nitride layer 14′, more preferably at least about20 Å or 25 Å thinner.

In certain example embodiments of this invention, coated articles hereinmay have the following optical and solar characteristics set forth inTable 2 when measured monolithically. The sheet resistances (R_(S))herein take into account all IR reflecting layers (e.g., silver layers9, 19).

Optical/Solar Characteristics (Monolithic; pre-HT) CharacteristicGeneral More Preferred Most Preferred R_(s) (ohms/sq.): <=3.5 <=2.5<=2.2 E_(n): <=0.07 <=0.04 <=0.03 T_(vis) (Ill, C 2°): 20-45% 20-43%24-36% R_(f)Y (Ill. C, 2 deg.): <=29% <=26% <=24% R_(g)Y (Ill. C, 2deg.): <=25% <=22% <=18%

In certain example embodiments, coated articles herein may have thefollowing characteristics, measured monolithically for example, afterheat treatment (HT):

Optical/Solar Characteristics (Monolithic; post-HT) CharacteristicGeneral More Preferred Most Preferred R_(s) (ohms/sq.): <=3.0 <=2.1<=1.9 E_(n): <=0.07 <=0.04 <=0.03 T_(vis) (Ill. C 2°): 20-45% 20-43%24-36% R_(f)Y (Ill. C, 2 deg.): <=29% <=26% <=24% R_(g)Y (Ill. C, 2deg.): <=25% <=22% <=18%

Moreover, in certain example laminated embodiments of this invention,coated articles herein which have been optionally heat treated to anextent sufficient for tempering, and which have been coupled to anotherglass substrate to form an IG unit, may have the following IG unitoptical/solar characteristics in a structure as shown in FIG. 2 (e.g.,where the two glass sheets are 4 mm thick and 6 mm thick respectively ofclear glass with a 16 mm gap therebetween filled with 90/10 argon/air).It can be seen that the film side reflection increases when placed in anIG window unit.

Example Optical Features (IG Unit pre or post-HT) Characteristic GeneralMore Preferred T_(vis) (or TY)(Ill. C 2°): 18-45% 20-33% a*_(t) (Ill. C2°): −9 to +1.0 −7 to 0.0 b*_(t) (Ill. C 2°): −10 to +10 −5 to +5 R_(f)Y(Ill. C, 2 deg.): <=31% <=28% a*_(f) (Ill. C, 2°): −6 to +8 −4 to +4b*_(f) (Ill. C, 2°): −6 to +12 −2 to +9 R_(g)Y (Ill. C, 2 deg.): 10-30%15-25% a*_(g) (Ill. C, 2°): −7 to +4 −5 to +1 b*_(g) (Ill. C, 2°): −16to +5 −14 to 0

The following examples are provided for purposes of example only, andare not intended to be limiting unless specifically claimed.

EXAMPLES

The following Example 1 was made via sputtering on 6 mm thick clearglass substrate so as to have approximately the layer stack set forthbelow. Example 1 is according to example embodiments of this inventionas shown in FIG. 1, whereas the Comparative Example (CE) below has anNiCr absorbing layer only in the middle of the stack and is provided forpurposes of comparison. Example 1 had approximately the following layerstack, where the thicknesses are in units of angstroms (Å), and the NiCrabsorbing layers 4 and 25 were slightly nitrided.

Example 1

Layer Glass (6 mm thick) Thickness (Å) Si_(x)N_(y) (layer 3) 419 ÅZnO_(x) (layer 7) 80 Å Ag (layer 9) 119 Å NiCrO_(x) (layer 11) 25 Å SnO₂(layer 13) 545 Å Si_(x)N_(y) (layer 14) 120 Å NiCr (layer 4) 62 ÅSi_(x)N_(y) (layer 14′) 151 Å SnO₂ (layer 15) 80 Å ZnO_(x) (layer 17) 80Å Ag (layer 19) 153 Å NiCr (layer 25) 35 Å Si₃N₄ (layer 26) 317 Å

The Comparative Example (CE) had a NiCr absorbing layer similar to thosein Example 1, but in the CE the sole absorbing layer was located only inthe middle stack between the silver layers. The CE had the followinglayer stack from the glass outwardly.

COMPARATIVE EXAMPLE Layer Glass (6 mm thick) Thickness (Å) Si_(x)N_(y)257 Å ZnO_(x) 100 Å Ag 77 Å NiCrO_(x) 25 Å SnO₂ 530 Å Si_(x)N_(y) 120 ÅNiCr 134 Å Si_(x)N_(y) 151 Å SnO₂ 80 Å ZnO_(x) 80 Å Ag 197 Å NiCrO_(x)25 Å SnO₂ 142 Å Si_(x)N_(y) 210 Å

Set forth below are the optical characteristics of Example 1 compared tothose of the Comparative Example (CE), measured monolithically post-HT.

COMPARISON BETWEEN EXAMPLE 1 AND COMPARATIVE EXAMPLE Characteristic Ex.1 Comparative Example T_(vis) (or TY)(Ill. C 2°): 32.3% 41.5% a*_(t)(Ill. C 2°): −5.1 −7.0 b*_(t) (Ill. C 2°): +0.2 −2.5 R_(f)Y (Ill. C, 2deg.): 22.3% 32.3% a*_(f) (Ill. C, 2°): −1.7 +6.5 b*_(f) (Ill. C, 2°):+9.8 +11.0 R_(g)Y (Ill. C, 2 deg.): 16.2% 14.5% a*_(g) (Ill. C, 2°):−1.1 −2.1 b*_(g) (Ill. C, 2°): −11.8 −10.2

It can be seen from the above that Example 1 had surprisingly superior(lower) visible film side reflectance (R_(f)Y) than the ComparativeExample (CE), even though Example 1 also had lower visible transmission(TY) than the CE, namely 22.3% in Example 1 compared to 32.3% in the CE.Thus, absorbing layers 4 and 25 in the middle and upper portions of thelow-E coating in Example 1 (as opposed to only in the center portion asin the CE), coupled with removing the tin oxide layer from the CE'supper dielectric stack, surprisingly caused the low-E coating to have acombination of both (i) a low visible transmission, and (ii) low visiblefilm side reflectance. The layer thicknesses of Example 1 alsosurprisingly allowed more desirable optical characteristics to berealized, compared to the CE.

In certain example embodiments of this invention, there is provided acoated article including a coating 30 supported by a glass substrate 1,the coating comprising: first and second infrared (IR) reflecting layers9 and 19 comprising silver, wherein said IR reflecting layers 9 and 19are spaced apart from one another, and wherein the first IR reflectinglayer 9 is located closer to the glass substrate 1 than is the second IRreflecting layer 19; a first substantially metallic or metallicabsorption layer 4 comprising Ni and/or Cr located such that the firstabsorption layer 4 is located between the first and second IR reflectinglayers 9 and 19, wherein the first absorption layer 4 is sandwichedbetween and contacting first and second dielectric layers 14 and 14′comprising or consisting essentially of silicon nitride; and a secondsubstantially metallic or metallic absorption layer 25 comprising Niand/or Cr located such that both the first and second IR reflectinglayers 9, 19 are located between the glass substrate 1 and the secondabsorption layer 25, wherein the second absorption layer 25 is locatedbetween and contacting the second IR reflecting layer 19 and a thirddielectric layer 26 comprising silicon nitride.

In the coated article of the immediately preceding paragraph, said firstand/or second absorption layers may each comprise or consist essentiallyof NiCr and/or NiCrN_(x).

In the coated article of any of the preceding two paragraphs, said firstand/or second absorption layers may each comprise from 1-15% nitrogen(atomic %).

In the coated article of any of the preceding three paragraphs, saidfirst and second IR reflecting layers are spaced apart by at least,moving away from the glass substrate: a layer comprising tin oxide 13,said first layer comprising silicon nitride 14, said first absorptionlayer 4, said second dielectric layer comprising silicon nitride 14′,another layer comprising tin oxide 15, and a layer comprising zinc oxide17.

In the coated article of any of the preceding four paragraphs, incertain example embodiments no metallic or substantially metallicabsorption layer is located between the first IR reflecting layer andthe glass substrate.

In the coated article of any of the preceding five paragraphs, incertain example embodiments only two IR reflecting layers comprisingsilver are contained in the coating.

In the coated article of any of the preceding six paragraphs, the firstabsorption layer may be from about 35-75 angstroms (Å) thick.

In the coated article of any of the preceding seven paragraphs, thesecond absorption layer may be from about 23-48 angstroms (Å) thick.

In the coated article of any of the preceding eight paragraphs, thefirst absorption layer may be substantially thicker than the secondabsorption layer.

In the coated article of any of the preceding nine paragraphs, saidcoated article may have a visible transmission of from about 20-43%(more preferably from about 24-36%), measured monolithically.

In the coated article of any of the preceding ten paragraphs, the coatedarticle may be thermally tempered, or not heat treated.

In the coated article of any of the preceding eleven paragraphs, thecoating in certain example embodiments may contain no more than twometallic or substantially metallic absorption layers consistingessentially of NiCr or NiCrN_(x).

In the coated article of any of the preceding twelve paragraphs, thethird layer comprising silicon nitride may be an uppermost layer of thecoating.

In the coated article of any of the preceding thirteen paragraphs, saidfirst IR reflecting layer and said first absorption layer may be spacedapart by at least, moving away from the glass substrate: a layercomprising an oxide of NiCr, a layer comprising tin oxide, and the firstlayer comprising silicon nitride.

In the coated article of any of the preceding fourteen paragraphs, thecoated article may have a visible film side reflectance (RfY), measuredmonolithically, of less than or equal to 26%, more preferably less thanor equal to 24%.

In the coated article of any of the preceding fifteen paragraphs, asubstantially oxided layer comprising an oxide of NiCr may be locatedover and directly contacting the first IR reflecting layer.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

The invention claimed is:
 1. A coated article including a coatingsupported by a glass substrate, the coating comprising: first and secondinfrared (IR) reflecting layers comprising silver, wherein said IRreflecting layers are spaced apart from one another, and wherein thefirst IR reflecting layer is located closer to the glass substrate thanis the second IR reflecting layer; a first substantially metallic ormetallic absorption layer comprising Ni and/or Cr located such that thefirst absorption layer is located between the first and second IRreflecting layers, wherein the first absorption layer is sandwichedbetween and contacting first and second dielectric layers comprisingsilicon nitride; a second substantially metallic or metallic absorptionlayer comprising Ni and/or Cr located such that both the first andsecond IR reflecting layers are located between the glass substrate andthe second absorption layer, wherein the second absorption layer islocated between and contacting the second IR reflecting layer and athird dielectric layer comprising silicon nitride; and wherein saidfirst and second substantially metallic or metallic absorption layerseach comprise from 0-5% oxygen.
 2. The coated article of claim 1,wherein said first and second absorption layers each comprise NiCr. 3.The coated article of claim 1, wherein said first and second absorptionlayers each comprise NiCrN_(x).
 4. The coated article of claim 1,wherein said first and second absorption layers each comprise from 1-15%nitrogen (atomic %).
 5. The coated article of claim 1, wherein saidfirst and second IR reflecting layers are spaced apart by at least,moving away from the glass substrate: a layer comprising tin oxide, saidfirst layer comprising silicon nitride, said first absorption layer,said second dielectric layer comprising silicon nitride, another layercomprising tin oxide, and a layer comprising zinc oxide.
 6. The coatedarticle of claim 1, wherein no metallic or substantially metallicabsorption layer is located between the first IR reflecting layer andthe glass substrate.
 7. The coated article of claim 1, wherein only twoIR reflecting layers comprising silver are contained in the coating. 8.The coated article of claim 1, wherein the first absorption layer isfrom about 35-75 angstroms (Å) thick.
 9. The coated article of claim 1,wherein the second absorption layer is from about 23-48 angstroms (Å)thick.
 10. The coated article of claim 1, wherein the first absorptionlayer is substantially thicker than the second absorption layer.
 11. Thecoated article of claim 1, wherein said coated article has a visibletransmission of from about 20-43%, measured monolithically.
 12. Thecoated article of claim 1, wherein said coated article has a visibletransmission of from about 24-36%, measured monolithically.
 13. Thecoated article of claim 1, wherein the coated article is thermallytempered.
 14. The coated article of claim 1, wherein the coated articleis not heat treated.
 15. The coated article of claim 1, wherein thecoating contains no more than two metallic or substantially metallicabsorption layers consisting essentially of NiCr or NiCrN_(x).
 16. Thecoated article of claim 1, wherein the third layer comprising siliconnitride is an uppermost layer of the coating.
 17. The coated article ofclaim 1, wherein said first IR reflecting layer and said firstabsorption layer are spaced apart by at least, moving away from theglass substrate: a layer comprising an oxide of NiCr, a layer comprisingtin oxide, and the first layer comprising silicon nitride.
 18. Thecoated article of claim 1, wherein the coated article has a visible filmside reflectance (RfY), measured monolithically, of less than or equalto 26%.
 19. The coated article of claim 1, wherein the coated articlehas a visible film side reflectance (RfY), measured monolithically, ofless than or equal to 24%.
 20. The coated article of claim 1, wherein asubstantially oxided layer comprising an oxide of NiCr is located overand directly contacting the first IR reflecting layer.
 21. The coatedarticle of claim 1, wherein a metallic or substantially metallic layercomprising NiCr and/or NiCrN_(x) is located over and directly contactingthe first IR reflecting layer.
 22. A coated article including a coatingsupported by a glass substrate, the coating comprising: first and secondinfrared (IR) reflecting layers, wherein said IR reflecting layers arespaced apart from one another, and wherein the first IR reflecting layeris located closer to the glass substrate than is the second IRreflecting layer; a first substantially metallic or metallic absorptionlayer located such that the first absorption layer is located betweenthe first and second IR reflecting layers, wherein the first absorptionlayer is sandwiched between and contacting first and second dielectriclayers comprising silicon nitride; a second substantially metallic ormetallic absorption layer located such that both the first and second IRreflecting layers are located between the glass substrate and the secondabsorption layer, wherein the second absorption layer is located betweenand contacting the second IR reflecting layer and a third dielectriclayer comprising silicon nitride; and wherein said first and secondsubstantially metallic or metallic absorption layers each comprise from0-5% oxygen.